CN-117787114-B - Turbulent combustion simulation method for temperature and pressure self-adaption of scramjet engine

CN117787114BCN 117787114 BCN117787114 BCN 117787114BCN-117787114-B

Abstract

The invention relates to a turbulent combustion simulation method for self-adapting temperature and pressure of a scramjet engine, which comprises the steps of constructing a flame surface database, estimating a database construction temperature and a pressure range of a target combustion flow field, wherein the database construction temperature comprises the minimum temperature and the maximum temperature of an oxidant end, the minimum temperature and the maximum temperature of a fuel end, determining four groups of estimated working conditions, solving a flame surface equation to obtain four groups of laminar flame surface solutions, carrying out ensemble averaging on the four groups of laminar flame surface solutions by adopting a set PDF function to obtain four groups of ensemble averaging solutions on the laminar flame surface solutions, selecting a reference flame surface database based on the ensemble averaging solutions of the groups, respectively obtaining scaling coefficients of all databases in the groups relative to the reference flame surface database, constructing the flame surface database by the reference flame surface database and the scaling coefficients, carrying out CFD calculation on the flow field of the scramjet engine, and updating a local flame surface database by the flame surface database after each calculation is finished.

Inventors

WANG HONGBO
SUN MINGBO
TANG TAO
XIONG DAPENG
ZHAO GUOYAN
YANG YIXIN

Assignees

中国人民解放军国防科技大学

Dates

Publication Date: 20260505
Application Date: 20221117

Claims (3)

1. A turbulent combustion simulation method for temperature and pressure adaptation of a scramjet engine, comprising the steps of: S1, constructing a flame surface database; Estimating a library building temperature and a pressure range of a target combustion flow field, wherein the library building temperature comprises a minimum temperature T ox1 and a maximum temperature T ox2 of an estimated oxidant end, a minimum temperature T fuel1 and a maximum temperature T fuel2 of a estimated fuel end, and n pressure values are uniformly dispersed in the pressure range and are respectively P 1 ,P 2 ,…,P n ; Four groups of estimated working conditions are determined based on the library building temperature and the pressure range, wherein the four groups of estimated working conditions are constructed based on the minimum temperature T ox1 and the maximum temperature T ox2 of the estimated oxidant end, the minimum temperature T fuel1 and the maximum temperature T fuel2 of the estimated fuel end, and n pressures P 1 ,P 2 ,…,P n in the pressure range are constructed in a combined way and are respectively expressed as: 、、 And , wherein, ; Solving flame surface equations under four groups of estimated working conditions to obtain four groups of laminar flame surface solutions; Carrying out ensemble averaging on four groups of laminar flame surface solutions by adopting a set PDF (portable document format) function to obtain four groups of ensemble average solutions related to the laminar flame surface solutions; Selecting a reference flame surface database based on the ensemble average solutions of each group, and respectively obtaining scaling coefficients of each database in the group relative to each reference flame surface database; constructing a flame face database based on the reference flame face database and the scaling factor; S2, carrying out CFD calculation on a flow field of the scramjet engine, and updating a local flame surface database based on the flame surface database after each calculation is finished, wherein the method comprises the following steps: After each step of CFD calculation is finished, counting the average temperature of an extremely lean combustion area as an oxidant end approximate temperature, and marking as T ox_count , and counting the average temperature of an extremely rich combustion area as a fuel end approximate temperature, and marking as T fuel_count , wherein an area with a mixing fraction in the range of 1E-5< Z <1E-4 is used as the extremely lean combustion area, and an area with a mixing fraction in the range of Z >0.25 is used as the extremely rich combustion area; Obtaining four flame face matching databases matched with the local pressure based on the flame face database and according to the linear interpolation of the local pressure; constructing weight factors for the four flame face matching databases according to the obtained oxidant end approximate temperature and the obtained fuel end approximate temperature, wherein the weight factors are respectively expressed as: Wherein, T ox1 <T ox_count <T ox2 and T fuel1 <T fuel_count <T fuel2 ; obtaining the local flame face database by linear weighting based on the weight factors and the flame face matching database, wherein the local flame face database is expressed as: Wherein, the Representing the local flame front database, Respectively representing four flame face matching databases.
2. The turbulent combustion simulation method according to claim 1, wherein in step S1, in the step of solving the flame surface equations under four sets of estimated working conditions to obtain four sets of laminar flame surface solutions, FLAMEMASTER is adopted to solve the flame surface equations, and the four sets of laminar flame surface solutions are respectively expressed as: wherein Z represents a mixing score and C represents a progress variable; in the step of performing ensemble averaging on four groups of laminar flame surface solutions by adopting a set-type PDF function to obtain four groups of ensemble average solutions related to the laminar flame surface solutions, a beta PDF function is adopted for the mixing score, a delta PDF is adopted for the progress variable, and the four groups of obtained ensemble average solutions are respectively expressed as: ; wherein, the superscript ". The result after ensemble averaging is shown.
3. The turbulent combustion simulation method according to claim 2, wherein in step S1, a reference flame surface database is selected based on each group of the ensemble average solutions, and scaling coefficients of each of the databases in the group with respect to each of the reference flame surface databases are obtained, respectively, where the reference flame surface databases are: The scaling coefficients are respectively: The scaling factor and the reference flame face database satisfy: 。

Description

Turbulent combustion simulation method for temperature and pressure self-adaption of scramjet engine Technical Field The invention relates to the field of Computational Fluid Dynamics (CFD), in particular to a turbulent combustion simulation method for temperature and pressure self-adaption of a scramjet engine. Background In recent years, hypersonic aircraft technology has become a hotspot for research and attention of various aviation aerospace countries in the world, but due to limitations of experimental technology and rapid development of large-scale computing power, computing combustion has become an effective means for researching flow and combustion inside a scramjet engine. One key technology of numerical simulation of the scramjet engine is simulation of turbulent combustion process, and two types of combustion models are mainly a PDF model and a flame surface model at present. The former is characterized by complete theoretical method, but the numerical processing is difficult and the calculated amount is large, and the latter flame surface model has the characteristics of physical intuitionism, high efficiency and accuracy in calculation, so that the model is widely applied. However, since the flame face model is derived from a low velocity diffusion flame, although subjected to the compression correction of Oevermann et al, the entire supersonic flow field is described by the solution of the flame face equation under single fixed temperature and pressure conditions, and the approximation is obviously rough for the combustion flow field of the scramjet engine with severe temperature and pressure changes. Therefore, the existing flame surface method cannot adaptively select the warehouse-building temperature and cannot deal with the non-uniform influence of pressure, and has obvious limitation on simulation of turbulent combustion process in the scramjet engine. As shown in fig. 1, the temperature and pressure of the supersonic incoming flow gradually rise under the action of the oblique shock wave or the precombustion shock wave string after entering the isolation section, and the average temperature in the extremely lean combustion area in fig. 1 can be approximate to the temperature before the incoming flow enters the reaction zone. The temperature of the under-expanded fuel jet after injection into the combustion chamber and partial blending with the incoming stream also deviates very rapidly from the injection temperature, and the average temperature in the very rich region of FIG. 1 can also be approximated as the temperature of the fuel stream prior to entering the reaction zone. In addition, the pressures at different locations within the combustion chamber are different, and thus the corresponding chemical reaction rates are also different. In order to accurately and adaptively describe such supersonic combustion flow fields, pressure and temperature dependent corrections to the flame face model are needed. Disclosure of Invention The invention aims to provide a turbulent combustion simulation method for temperature and pressure self-adaption of a scramjet engine. In order to achieve the above object, the present invention provides a turbulent combustion simulation method for temperature and pressure adaptation of a scramjet engine, comprising the steps of: S1, constructing a flame surface database; Estimating a library building temperature and a pressure range of a target combustion flow field, wherein the library building temperature comprises a minimum temperature T ox1 and a maximum temperature T ox2 of an estimated oxidant end, a minimum temperature T fuel1 and a maximum temperature T fuel2 of a estimated fuel end, and n pressure values are uniformly dispersed in the pressure range and are respectively P 1,P2,…,Pn; determining four groups of estimated working conditions based on the warehouse building temperature and the pressure range; Solving flame surface equations under four groups of estimated working conditions to obtain four groups of laminar flame surface solutions; Carrying out ensemble averaging on four groups of laminar flame surface solutions by adopting a set PDF (portable document format) function to obtain four groups of ensemble average solutions related to the laminar flame surface solutions; Selecting a reference flame surface database based on the ensemble average solutions of each group, and respectively obtaining scaling coefficients of each database in the group relative to each reference flame surface database; constructing a flame face database based on the reference flame face database and the scaling factor; S2, carrying out CFD calculation on the flow field of the scramjet engine, and updating a local flame surface database based on the flame surface database after each calculation is finished. According to one aspect of the present invention, in the step of determining four sets of estimated conditions based on the library temperature and the pressure ran